Isomer-Directed Structural Diversity and Its Effect on the Nanosheet Exfoliation and Magnetic Properties of 2,3-Dimethylsuccinate Hybrid Frameworks

Abstract

The structures of seven new transition metal frameworks featuring Mn, Co, or Zn and either the meso or chiral D and L isomers of the 2,3-dimethylsuccinate ligand are reported. Frameworks that exhibit two-dimensional covalently bonded layers with weak interlayer interactions can be made with all three cations by incorporation of the chiral isomers of the 2,3-dimethylsuccinate ligand. The formation of such structures, suitable for the creation of nanosheets via exfoliation, is, however, not as ubiquitous as is the case with the 2,2-dimethylsuccinate frameworks since frameworks that incorporate the meso-2,3-dimethylsuccinate ligand form three-dimensional structures. This clear distinction between the formation of structures with covalent connectivity in two and three dimensions, depending on the choice of 2,3-dimethylsuccinate isomer, is due to the different conformations adopted by the backbone of the ligand. The chiral isomer prefers to adopt an arrangement with its methyl and carboxylate groups gauche to the neighboring functional groups of the same type, while the meso-ligand prefers to adopt trans geometry. A gauche-arrangement of the methyl groups places them on the same side of the ligand, making this geometry ideal for the formation of layered structures; a trans-relationship leads to the methyl groups being further apart, reducing their steric hindrance and making it easier to accommodate them within a three-dimensional structure. The ease of exfoliation of the layered frameworks is examined and compared to those of known transition metal 2,2-dimethylsuccinate frameworks by means of UV-vis spectroscopy. It is suggested that layered frameworks with more corrugated surfaces exfoliate more rapidly. The size, structure, and morphology of the exfoliated nanosheets are also characterized. The magnetic properties of the paramagnetic frameworks reveal that only the three dimensionally covalently bonded phases containing meso-2,3-DMS in trans-arrangements order magnetically. These frameworks are antiferromagnets at low temperatures, although the Co compound undergoes an unusual antiferromagnetic to ferromagnetic transition with increasing applied magnetic field.

Recent Advances on Anilato-Based Molecular Materials with Magnetic and/or Conducting Properties

“…The solution-based exfoliation procedure is less effective in the neutral coordination polymers which can be completely delaminated (with a thickness ca. 1-1.5 nm) [115,170,[176][177][178][179][180][181][182][183]. The stronger interlayer interactions in these hybrid compounds compared with the weaker van der Waals interactions observed in neutral 2D coordination polymers could be responsible of the lower degree of exfoliation.…”

One-dimensional magnetic order in the metal-organic framework Tb(HCOO)3

“…chains, ladders, layers), MOFs are natural candidate hosts for low-dimensional magnetism [18]. Indeed the magnetic response of a number of key MOF familiesincluding formates [19], oxalates [20], and succinates [21,22]-can be interpreted in terms of low-dimensional behaviour. However, nearly all of our collective understanding of magnetic order in MOFs is based on indirect experimental techniques, such as magnetic susceptibility, heat capacity, and dielectric constant measurements [19][20][21][22][23].…”

“…Indeed the magnetic response of a number of key MOF familiesincluding formates [19], oxalates [20], and succinates [21,22]-can be interpreted in terms of low-dimensional behaviour. However, nearly all of our collective understanding of magnetic order in MOFs is based on indirect experimental techniques, such as magnetic susceptibility, heat capacity, and dielectric constant measurements [19][20][21][22][23]. Tb(HCOO) 3 is a notable exception: it is one of the few MOFs for which neutron scattering measurements have been used to characterise magnetic structure within both antiferromagnetic (T < T N 1.6 K) and paramagnetic (T = 3 K) regimes [24,25].…”

Chirality‐ and pH‐Controlled Supramolecular Isomerism in Cobalt Phosphonates and Its Impact on the Magnetic Behavior

“…Compared with those in (S)-1,h owever,t he structural parameters of the chain in (S)-2 are slightly different (Table 3). If the Co1, Co2, (6) . Them ost significant feature of the structure of (S)-2 is that each chain is connected to two other equivalent chains through 4,4'-bpy bridges, whereas in (S)-1 each chain is linked to four othere quivalents by 4,4'-bpy (Supporting Information, Figure S6).…”

“…However,t here are only ah andfulo fr eports on comparative studies of homochiral and racemic inorganic-organic hybrid materials or metal-organic frameworks (MOFs) so far. [5][6][7][8][9] In this aspect, am ajor challenge is to isolate single crystals of both the chiral and racemic speciesb ased on the same ligand, whichi so ften very difficult. Lin et al found that the interpenetration of MOFs can be controlled by using enantiopure or racemic bridging ligands that further affectt he pore size and framework rigidity.…”